People often blame food additives like dyes, preservatives, emulsifiers and flavor enhancers for chronic hives and other allergic reactions. But a new randomized trial shows that they are almost surely wrong. Over 10 years, researchers conducted "oral challenge" tests (in which patients ingest a suspect food and wait for a reaction) on 100 people who had been suffering from skin irritations with no known cause for six weeks or longer, called chronic urticaria.